Hard disk drives (HDDs), as an example of a disk device, comprise, for example, a magnetic disk disposed in a casing, spindle motor configured to support and rotate the magnetic disk, actuator assembly supporting a magnetic head, voice coil motor configured to drive the actuator assembly, and flexible printed circuit unit (hereinafter referred to as FPC unit).
The actuator assembly comprises an actuator block including a plurality of arms and a unit bearing attached to an attachment hole of the actuator block. To each arm, one or two suspension assemblies supporting the magnetic head are attached. The unit bearing is, for example, a combination of two ball bearings and a spacer. The bearings are greased to reduce friction and wearing.
During a seek operation by the actuator assembly, grease or lubricant may be splashed from between inner and outer rings of the bearings. The splashing grease may be leaked or added to the magnetic disk and the magnetic head to cause insufficient flying and crushing of the magnetic head, and thereby results in a great problem such as read/write error. To prevent this, the upper part of the unit bearing is covered with a cap and the lower part thereof is covered with a shaft base to block splashing grease.
In recent years, storage capacity of HDD is increased, and accordingly, the number of magnetic disks disposed therein is increased. In order to deal with a number of magnetic disks, a so-called dual actuator assembly including two or more actuator assembles is proposed. In the dual actuator assembly, two unit bearings are disposed one-on-another in the axis direction with a spacer therebetween. In that case, a grease splashing space (gap) which is difficult to be adjusted by the cap and shaft base is formed between two unit bearings. Thus, grease splash from the unit bearings may possibly be increased.